The applicant has developed a paste-like bonding member containing a low melting point metal and a high melting point metal (see, for example, Patent Document 1). When the bonding member is heated to a predetermined temperature, the low melting point metal is melted to react with the high melting point metal and thus to form an intermetallic compound having a melting point higher than that of the low melting point metal. When the intermetallic compound is formed, the amount of the low melting point metal or the high melting point metal is reduced, or additives such as a binder are evaporated and vaporized, so that a joint portion formed from the bonding member becomes a porous portion including many voids.
Meanwhile, a bonding member (see, for example, Patent Document 2) capable of providing a joint portion having a dense structure rather than porous structure has also been developed. The bonding member is formed into a sheet shape by rolling or hot pressing high melting point metal particles sandwiched between metal foils formed of low melting point metal to bind the high melting point metal particles. In a joint portion formed from the bonding member, the low melting point metal of the metal foil melts and fills voids of an intermetallic compound, so that it is possible to obtain a dense structure in which voids hardly remain. There is also a case where metal particles are caused to remain in a joint portion, thereby increasing the minimum thickness of the joint portion and securing a stand-off height of a component to be bonded (see, for example, Patent Document 3).
Patent Document 1: Japanese Patent No. 5018978
Patent Document 2: Japanese Patent Application Laid-Open No. 2002-301588
Patent Document 3: Japanese Patent Application Laid-Open No. 2013-212524